The present disclosure relates to prosthetic heart valve replacement and, in particular, delivery systems and introducers for use with prosthetic heart valves.
Prosthetic heart valves that are collapsible to a relatively small circumferential size can be delivered into a patient less invasively than valves that are not collapsible. For example, a collapsible valve may be delivered into a patient via a tube-like delivery apparatus such as a catheter, a trocar, a laparoscopic instrument, or the like. This collapsibility can avoid the need for a more invasive procedure such as full open-chest, open-heart surgery.
Collapsible prosthetic heart valves typically take the form of a valve structure mounted on a stent. There are two types of stents on which the valve structures are ordinarily mounted: a self-expanding stent and a balloon-expandable stent. To place such valves into a delivery apparatus and ultimately into a patient, the valve must first be collapsed or crimped to reduce its circumferential size.
Generally, when implanting a prosthetic heart valve into a patient, an introducer sheath is first introduced into the desired blood vessel or other anatomy. This may occur after a guidewire and one or more dilators are introduced into the patient. The introducer sheath is advanced to the site of valve implantation, for example through the apex of the left ventricle to the desired heart valve annulus (transapical) or through the femoral artery to the desired heart valve annulus (transfemoral). As described in greater detail below, other delivery routes for heart valve replacement are possible. Once the introducer sheath is in place, it is used as a conduit to pass other devices, as necessary, from outside the patient to the site of implantation. For example, a delivery device containing the prosthetic heart valve in a collapsed condition may be passed through the introducer sheath so that the prosthetic heart valve may be deployed and implanted at the desired native heart valve annulus.
When the collapsed prosthetic valve has reached the desired implant site in the patient (e.g., at or near the annulus of the heart valve that is to be replaced by the prosthetic valve), the prosthetic valve can be deployed or released from the delivery apparatus and re-expanded to full operating size. For balloon-expandable valves, this generally involves releasing the entire valve, assuring its proper location, and then expanding a balloon positioned within the valve stent. For self-expanding valves, on the other hand, the stent automatically expands as the sheath covering the valve is withdrawn.
Generally, introducer sheaths have elongated portions with a hollow core to allow passage of devices through the introducer sheath. Often, the hollow core of the introducer sheath has a diameter that is larger than the largest device that would be passed through the introducer sheath. However, it is generally desired to have the smallest possible diameter for an introducer sheath to accommodate the small and often tortuous anatomy of the vasculature or other delivery route through the body. Additionally, despite different possible routes of delivery, introducer sheaths often have little or no route-dependent variation. It would thus further be desirable to have a single introducer sheath design that could better facilitate delivery of a prosthetic heart valve via different delivery routes.